Apparatus and method for measuring speed of a moving object

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention generally relates to an apparatus and method for measuring the speed of a moving object, and in particular, to an apparatus and method for measuring the speed of these moving objects based on a roll angle.

2. Description of the Related Art

[0002] Generally, moving objects such as vehicles, ships, and aircrafts have an embedded navigation system that determines the position of the moving object (positioning), routes a path to a given destination (routing), and provides the routing results.

[0003] In order to determine the position of a moving object and provide a path to the destination, navigation systems should be able to determine the exact position of a vehicle. Therefore, navigation systems generally include a positioning device for position determination. Such positioning devices are classified into two types, one for determining the position using an outside source and the other for determining the position using an inside sensor. A Global Positioning System (GPS) is an example of the former type of positioning device. A Dead Reckoning (DR) system using an inertial sensor is an example of the latter type of positioning device.

[0004] A DR system calculates the speed and position of a moving object using a gyroscope for detecting a rotational motion of the moving object and an accelerometer for detecting a straight line motion of the moving object. In particular, the speed of the moving object can be calculated using both speed information acquired from an acceleration measured by the accelerometer and moving direction information acquired from the gyroscope.

[0005] In general, the DR system measures the moving direction angle of a vehicle on a road and an acceleration in the moving direction of the vehicle, as well as calculates the moving speed vector of the vehicle using the moving direction angle of the vehicle and the acceleration in the moving direction of the vehicle. In order to measure the moving direction of the vehicle, the DR system requires a gyroscope installed on an axis perpendicular to a plane on which wheel axles(axis of axles) are placed. And in order to measure the acceleration in the moving direction of the vehicle, the DR system requires the measurement value of a road inclination angle in addition to an accelerometer installed in the direction of the wheel axle(axis of axle).

[0006] The road inclination angle measurement value is required because a specific force component proportional to gravitational acceleration is included in the output of the accelerometer and the specific force component may be calculated from the road inclination angle. Since gravitational acceleration works perpendicularly to the surface of the earth spheroid (a spherical surface perpendicular to the directions of the gravitational acceleration) at all times, the angle of the axis of the accelerometer mounted in the vehicle (fixed in a particular direction within the vehicle) with respect to the surface of the earth spheroid changes, thereby resulting in a change in the specific force component included in the output of the accelerometer.

[0007] In other words, if the road inclination angle changes, the direction of the axis of the accelerometer mounted in the vehicle is not perpendicular to the direction of gravitational acceleration. Thus, the accelerometer measures a rate of change in the actual speed of motion (an actual motional acceleration) including a component of gravitational acceleration.

[0008] FIG. 1 is a view explaining a component of the gravitational acceleration included in the acceleration of a moving object. Referring to FIG. 1, a road inclination angle is inclined with respect to a plane perpendicular to the direction (±g) of the gravitational acceleration. In FIG. 1, an angle between a plane 20 perpendicular to the direction (±g) of the gravitational acceleration and a plane 10 extending in the moving direction of a vehicle 30 is a road inclination angle θ. When the vehicle 30 travels on the plane 10 inclined at the road inclination angle θ with respect to the plane 10 perpendicular to the direction (±g) of the gravitational acceleration as shown in FIG. 1, a measurement value a of an accelerometer mounted in the vehicle 30 includes an actual acceleration and a component of a gravitational acceleration g. Thus, the component of the gravitational acceleration g is also measured together with a rate of change in the actual speed of motion and may cause a big error in the measurement of speed.

[0009] Thus, for accurate speed measurement, a vehicle DR system must subtract the gravitational acceleration g from the measurement value a of the accelerometer and measures the road inclination angle θ to measure the gravitational acceleration g.

[0010] The DR system for vehicles can measure the road inclination angle θ using a rotational angle with respect to the forward direction of a vehicle, a rotational angle with respect to the lateral direction of the vehicle perpendicular to the forward direction of the vehicle, and a rotational angle and a roll angle φ with respect to the lower direction of the vehicle perpendicular to the forward direction and the lateral direction of the vehicle. The roll angle φ means the amount of inclination of the vehicle with respect to the forward direction of the vehicle.

[0011] FIG. 2 illustrates coordinate axes defined in a moving object. In FIGs. 2A and 2B, an axis along the forward direction of a vehicle is defined as an X axis, an axis perpendicular to the X axis and passing through the lateral sides of the vehicle is defined as a Y axis, and an axis perpendicular to an XY plane along the lower direction of the vehicle is defined as a Z axis.

[0012] Referring to FIG. 2, a rate of change in the road inclination angle θ can be expressed in Equation (1) as follows:

where ω_Y is an angular speed along the Y axis, ω_Z is an angular speed along the Z axis, and φ is the roll angle of the vehicle. At this time, the roll angle φ means the angle of inclination of the vehicle along the X axis.

[0013] The change rate of the roll angle φ can be expressed in Equation (2) as follows:

where ω_X is an angular speed along the X axis. Equations (1) and (2) are well-known relational expressions related to the change rate of an Euler angle.

[0014] Referring to Equation (2), to accurately calculate the change rate

of the roll angle φ, three axis gyroscopes are required for measuring the angular speed ω_X along the X axis, the angular speed ω_Y along the Y axis, and the angular speed ω_Z along the Z axis.

[0015] However, generally, a roll motion that is a rotational motion with respect to a wheel axle(axis of axle) (the X axis) connecting the front and rear sides of the vehicle and a straight line motion with respect to an axis (the Z axis) perpendicular to the ground surface is negligible during driving of the vehicle. Thus, conventionally, the road inclination angle θ is calculated only using the angular speed ω_X along the X axis and the angular speed ω_Y along the Y axis, irrespective of the roll angle φ and the angular speed ω_Z along the Z axis in Equation (2).

[0016] When the roll angle φ and the angular speed ω_Z along the Z axis are neglected, i.e., they are assumed to be 0, Equation (1) is

and the change rate

of the road inclination angle θ can be given as in Equation (3) by:

where ω_Y can be calculated from the output of a gyroscope that measures an angular speed along an axis (the Y axis) passing through the lateral sides perpendicular to the forward direction of the vehicle and the road inclination angle θ is obtained by integrating ω_Y.

[0017] However, when there are many curves on the road and thus the roll angle of the vehicle increases, the roll angle of the vehicle has a significant influence upon the road inclination angle. In addition, when the angular speed ω_Z along the Z axis is large in Equation (1), even if the roll angle of the vehicle is not large, the roll angle of the vehicle has a significant influence upon the road inclination angle. As a result, conventional calculations of the road inclination angle θ, which neglects the roll angle of the vehicle, has a significant error.

[0018] In other words, in the case where the roll angle of the vehicle has a large influence upon the road inclination angle, the road inclination angle calculated using Equation (3) neglecting the roll angle of the vehicle has a difference with the actual road inclination angle, which increases over time. As a result, there are large differences between measured speed and position and actual speed and position. Thus, the road inclination angle should be calculated based on the roll angle of the vehicle.

[0019] In Equation (2), gyroscopes for the X axis, the Y axis, and the Z axis are required to calculate the change rate

of the roll angle φ based on the roll angle φ. However, to use the gyroscope for three axes, additional gyroscopes must be mounted in a DR system, increasing the manufacturing cost of the DR system for measuring the speed of the vehicle.

[0020] JP 2004 150973 A discloses the use of an acceleration detector in the direction of the longitudinal axis of a vehicle, an acceleration detector in a direction of the lateral axis of the vehicle, a roll rate sensor and a pitch rate sensor for calculating a pure longitudinal acceleration of the vehicle.

[0021] EP 1 096 230 A2 teaches a vehicular inertial guidance navigation system, which feeds the outputs of angular rate sensors and accelerometers to a Kalman filter via a frame transformation into the earth reference frame for the calculation of a pure acceleration of the vehicle.

[0022] US 2003/236606 A1 teaches a dynamic control system for vehicles, which can detect road side bank and slope angles.

[0023] US 5 935 191 A teaches a navigation apparatus using the output data of an acceleration detecting means for detecting vehicle acceleration.

[0024] US 2005/021270 A1 discloses a method for measuring the speed of a moving body using an accelerometer, which measures accelerations along the x- and y-axes and for calculating a moving average of the measured accelerations.

SUMMARY OF THE INVENTION

[0025] It is, therefore, an object of the present invention to provide an apparatus and method for measuring the speed of a moving object based on roll movement.

[0026] It is still another object of the present invention to provide an apparatus and method for measuring the speed of a moving object based on roll movement by using an accelerometer, instead of additionally mounting gyroscopes.

[0027] To achieve one aspect of the present invention, there is provided an apparatus for measuring the speed of a moving object. The apparatus includes accelerometers, gyroscopes, a roll angle calculator, an inclination angle calculator, and a speed calculator. The accelerometers measure a first acceleration along the moving direction of the moving object and a second acceleration along the lateral direction of the moving object. The gyroscopes measure a first angular speed along the lateral direction of the moving object and a second angular speed along the lower direction of the moving object. The roll angle calculator calculates the roll angle of the moving object using the second acceleration, the second angular speed, a previous speed of the moving object in the moving direction of the moving object, and a previous road inclination angle with respect to the moving direction of the moving object. The inclination angle calculator calculates a road inclination angle using the calculated roll angle, the first angular speed, and the second angular speed. The speed calculator calculates a pure motion acceleration in the moving direction of the moving object using the calculated road inclination angle and calculates the speed of the moving object using the pure motion acceleration of the moving object.

[0028] To achieve another aspect of the present invention, there is also provided a method for measuring the speed of a moving object. The method includes the steps of measuring a first acceleration along the moving direction of the moving object and a second acceleration along the lateral direction of the moving object, measuring a first angular speed along the lateral direction of the moving object and a second angular speed along the lower direction of the moving object, calculating the roll angle of the moving object using the second acceleration, the second angular speed, a previous speed of the moving object in the moving direction of the moving object, and a previous road inclination angle with respect to the moving direction of the moving object, calculating a road inclination angle using the calculated roll angle, the first angular speed, and the second angular speed, and calculating a pure motion acceleration in the moving direction of the moving object using the calculated road inclination angle and calculating the speed of the moving object using the pure motion acceleration of the moving object.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a view explaining a component of a gravitational acceleration included in the acceleration of a moving object;

FIG. 2A and 2B illustrates coordinate axes defined in a moving object;

FIG. 3 is a view explaining an arrangement of a gyroscope and an accelerometer in a moving object according to the present invention;

FIG. 4 is a block diagram of an apparatus for measuring the speed of a moving object according to the present invention;

FIG. 5 is a flowchart illustrating a method for measuring the speed of a moving object according to the present invention; and

FIGs. 6A, 6B, 7A and 7B illustrate the measured speeds of a moving object according to prior art and according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] A preferred embodiment of the present invention will now be described in detail with reference to the annexed drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for conciseness.

[0031] An apparatus for measuring the speed of a moving object according to the present invention calculates the roll angle of the moving object using two axis gyroscopes and two axis accelerometers and measures the speed of the moving object based on the calculated roll angle.

[0032] FIG. 3 is a view explaining an arrangement of a gyroscope and an accelerometer in a moving object according to the present invention. In FIG. 3, a moving object is a vehicle.

[0033] Referring to FIG. 3, an X axis is a wheel axis connecting the front and rear sides of the vehicle and is in parallel with the moving direction of the vehicle. A Y axis is perpendicular to the moving direction of the vehicle and passes through the lateral sides of the vehicle. A Z axis is perpendicular to the X axis and the Y axis and connects the top and the bottom of the vehicle.

[0034] According to the present invention, the apparatus for measuring the speed of a moving object includes two gyroscopes that are located on the Y axis and the Z axis perpendicularly to each other, and two accelerometers located on the X axis and the Y axis also perpendicularly to each other.

[0035] A Y-axis gyroscope located on the Y axis measures the angular speed ω_Y along the Y axis and a Z-axis gyroscope located on the Z axis measures the angular speed ω_Z along the Z axis. An X-axis accelerometer located on the X axis measures an acceleration f_x along the X axis and a Y-axis accelerometer located on the Y axis measures an acceleration f_Y along the Y axis.

[0036] When the constant of the gravitational acceleration is assumed to be g, the acceleration f_X along the X axis calculated by the X-axis accelerometer is expressed in Equation (4) as follows:

where a_X is an actual motion acceleration component of a moving object along the X axis, g is the constant of the gravitational acceleration, g sin θ is a gravitational acceleration component, and - ω_ZV_Y + ω_YV_Z is an acceleration component caused by a rotational motion of the moving object.

[0037] The acceleration f_Y along the Y-axis calculated by the X-axis accelerometer is expressed in Equation (5) as follows:

where a_Y is an actual motion acceleration component of a moving object along the Y axis, g is the constant of the gravitational acceleration, - g sinθφ cos θ is a gravitational acceleration component, and ω_ZV_X + ω_XV_Z is an acceleration component caused by a rotational motion of the moving object.

[0038] In Equations (4) and (5), ω_X is an angular speed along the X axis, ω_Y is an angular speed along the Y axis, ω_Z is an angular speed along the Z axis, V_X is a speed component along the X axis, V_Y is a speed component along the Y axis, and V_Z is a speed component along the Z axis.

[0039] Since the vehicle nearly moves along a straight line in the direction of the X axis, V_Y and V_Z in Equations (4) and (5) are close to 0. Thus, when V_Y and V_Z are assumed to be 0, the acceleration f_X along the X axis is expressed in Equation (6) as follows:

[0040] In order to acquire a gravitational acceleration component g sinθ included in the acceleration f_X along the X axis in Equation (6), the road inclination angle θ should be calculated first.

[0041] The road inclination angle θ can be calculated by integrating Equation (1), i.e.,

[0042] By integrating Equation (1), the road inclination angle θ at a time instant t is induced and expressed in Equation (7) as follows:

where θ₀ is the initial value of θ at time t = 0.

[0043] In order to calculate the road inclination angle θ in Equation (7), the roll angle φ should be acquired first. The roll angle φ can be calculated using Equation (5). When the acceleration component a_Y along the Y axis is assumed to be 0 in Equation (5), Equation (5) can be arranged as expressed in Equation (8) as follows:

f_Y can be expressed as in Equation (9) for the roll angle φ as follows:

where f_Y uses a measurement value of the Y-axis accelerometer, ω_Z uses a measurement value of the Z-axis gyroscope, a speed V_X along the X axis and the road inclination angle θ use their immediately previous estimates. The immediately previous estimates mean previous estimates V_X and θ. When there is no immediately previous estimate, predetermined initial values may be used.

[0044] By using the immediately previous estimates V_X and θ in Equation (9), the roll angle φ can be given by Equation (10) as follows:

[0045] By substituting a calculated roll angle estimate φ̂ into Equation (1), a road inclination angle change rate

is expressed in Equation (11) as follows:

[0046] By substituting a measurement value ω_Y of the Y-axis gyroscope and a measurement value ω_Z of the Z-axis gyroscope into Equation (11), the road inclination angle change rate

is calculated and is then integrated with respect to a time axis to acquire the road inclination angle θ.

[0047] The gravitational acceleration component gsinθ included in the acceleration measurement value f_X along the X axis in Equation (6) can be acquired using the calculated road inclination angle θ.

[0048] By subtracting the gravitational acceleration component gsinθ from the acceleration f_X along the X axis, a pure motion acceleration of the moving object along the X axis is acquired as expressed in Equation (12) as follows:

[0049] By integrating the pure motion acceleration a_X acquired using Equation (12) with respect to the time axis, a pure speed V_X of the moving object along the X axis can be acquired.

[0050] Thus, the apparatus for measuring the speed of a moving object according to the present invention can accurately measure a pure motion speed of the moving object using the principles described above.

[0051] Hereinafter, the configuration of the apparatus for measuring the speed of a moving object according to the present invention will be described in detail below. FIG. 4 is a block diagram of an apparatus for measuring the speed of a moving object according to the present invention. Referring to FIG. 4, the apparatus includes an X-axis accelerometer 110, a Y-axis accelerometer 120, a Y-axis gyroscope 130, a Z-axis gyroscope 140, a sensor data processor 150, a roll angle calculator 160, an inclination angle calculator 170, a speed calculator 180, and a data storage unit 190.

[0052] The X-axis accelerometer 110 measures a first acceleration, i.e., the acceleration f_X along the X axis. The Y-axis accelerometer 120 measures a second acceleration, i.e., the acceleration f_Y along the Y axis. The Y-axis gyroscope 130 measures a first angular speed, i.e., the angular speed ω_Y along the Y axis. The Z-axis gyroscope 140 measures a second angular speed, i.e., the angular speed ω_Z along the Z axis.

[0053] The sensor data processor 150 processes the acceleration measurement values f_X and f_Y output from the X-axis accelerometer 110 and the Y-axis accelerometer 120 and the angular speed measurement values ω_Y and ω_Z output from the Y-axis gyroscope 130 and the Z-axis gyroscope 140. In other words, the sensor data processor 150 corrects the acceleration measurement values f_X and f_Y and the angular speed measurement values ω_Y and ω_Z and provides correction data to the roll angle calculator 160.

[0054] The roll angle calculator 160 calculates the roll angle φ of a moving object using the acceleration measurement value f_Y along the Y axis, the angular speed measurement value ω_Z along the Z axis, a previous speed V_X along the X axis, and a previous road inclination angle θ. In other words, the roll angle calculator 160 arranges Equation (5) for the acceleration f_Y measured by the Y-axis accelerometer 120 to Equation (9) for the roll angle φ. The roll angle calculator 160 calculates the roll angle φ by substituting the acceleration measurement value f_Y along the Y axis, the angular speed measurement value ω_Z along the Z axis, the previous speed V_X along the X axis, and the previous road inclination angle θ into Equation (9). At this time, the previous speed V_X along the X axis and the previous road inclination angle θ are immediately previous estimates. The immediately previous estimates mean previous estimates V_X and θ. When there is no immediately previous estimate, predetermined initial values may be used.

[0055] The inclination angle calculator 170 calculates the road inclination angle θ using the roll angle φ calculated by the roll angle calculator 160, the angular speed ω_Y measured by the Y-axis gyroscope 130, and the angular speed ω_Z measured by the Z-axis gyroscope 140. In other words, the inclination angle calculator 170 acquires Equation (10) for the roll angle φ using immediately previous estimates V_X and θ and calculates a road inclination angle change rate using Equation (11) by substituting Equation (10) into Equation (1). The inclination angle calculator 170 substitutes the calculated roll angle φ, the angular speed ω_Y measured by the Y-axis gyroscope 130, and the angular speed ω_Z measured by the Z-axis gyroscope 140 into Equation (11) and integrates the road inclination angle change rate with respect to the time axis, thereby calculating the road inclination angle θ.

[0056] The speed calculator 180 calculates an accurate speed of the moving object using the road inclination angle θ calculated by the inclination angle calculator 170 and the acceleration measurement value f_X along the X axis. In other words, the speed calculator 180 calculates the gravitational acceleration component gsinθ in Equation (6) for the acceleration f_X by using the road inclination angle θ. The speed calculator 180 subtracts the gravitational acceleration component gsinθ from the acceleration measurement value f_X, thereby calculating the pure motion acceleration of the moving object along the X axis as in Equation (12).

[0057] The data storage unit 190 stores the road inclination angle θ calculated by the inclination angle calculator 170 and the pure speed V_X of the moving object calculated by the speed calculator 180 and provides the stored previous road inclination angle θ and the stored previous pure speed V_X of the moving object to the roll angle calculator 160. Thus, the roll angle calculator 160 can calculate the roll angle φ using the acceleration measurement value f_Y, the angular speed measurement value ω_Z , the previous pure speed V_X , and the previous road inclination angle θ.

[0058] Hereinafter, a method for measuring the speed of a moving object according to the present invention will be described in detail. FIG. 5 is a flowchart illustrating a method for measuring the speed of a moving object according to the present invention. Referring to FIG. 5, the acceleration measurement value f_Y is acquired in step 402 of FIG. 5. The acceleration measurement value f_Y is acquired by the Y-axis accelerometer 120 and indicates the amount of change in a speed along an axis (the Y axis) perpendicular to an axis (the X axis) along the forward direction of the moving object and passing through the lateral sides of the moving object.

[0059] In step 404 of FIG. 5, the angular speed measurement value ω_Z is acquired. The angular speed measurement value ω_Z is acquired by the Z-axis gyroscope 140 and indicates an angular speed along an axis (the Z axis) perpendicular to an XY plane along the lower direction of the moving object.

[0060] In step 406 of FIG. 5, the angular speed measurement value ω_Y is acquired. The angular speed measurement value ω_Y is acquired by the Y-axis gyroscope 130 and indicates an angular speed along an axis (the Y axis) passing through the lateral sides of the moving object.

[0061] After the acceleration measurement value f_Y and the angular speed measurement values ω_Z and ω_Y are acquired, the roll angle φ is calculated in step 408 of FIG. 5. Simply, the roll angle φ of the moving object is calculated using the acquired acceleration measurement value f_Y , the angular speed measurement value ω_Y , the previous speed V_X along the X axis, and the previous road inclination angle θ. An equation for the acceleration measurement value f_Y acquired by the Y-axis gyroscope 130 is arranged to an equation for the roll angle φ. The roll angle φ is then calculated by substituting the acceleration measurement value f_Y , the angular speed measurement value ω_Y, the previous speed V_X along the X axis, and the previous road inclination angle θ into the equation for the roll angle φ. At this time, the speed V_X along the X axis and the road inclination angle θ are immediately previous estimates. The immediately previous estimates are the previous estimates V_X and θ. When there is no immediately previous estimate, predetermined initial values may be used.

[0062] After calculation of the roll angle φ, the road inclination change rate is calculated in step 410 of FIG. 5. In other words, Equation (10) for the roll angle φ is acquired using the immediately previous estimates V_X and θ and the road inclination change rate is calculated using Equation (11) acquired by substituting Equation (10) into Equation (1).

[0063] In step 412 of FIG. 5, the road inclination change rate is integrated with respect to the time axis, thereby calculating the road inclination angle θ.

[0064] In step 414 of FIG. 5, a pure motion acceleration is calculated by subtracting a gravitational acceleration component from the acceleration measurement value f_X along the X axis. In other words, the gravitational acceleration component gsinθ is calculated using the calculated road inclination angle θ and the pure motion acceleration a_X is calculated by subtracting the gravitational acceleration component from the acceleration measurement value f_X .

[0065] In step 416 of FIG. 5, the pure speed V_X of the moving object along the X axis is calculated by integrating the pure motion acceleration a_X with respect to the time axis.

[0066] In other words, according to the present invention, the speed of a moving object can be accurately measured based on the roll angle of the moving object.

[0067] FIGs. 6A, 6B, 7A and 7B illustrate the speeds of a moving object measured according to prior art and according to the present invention. In FIGs. 6 and 7, the speed of a moving object measured irrespective of the roll angle of the moving object according to prior art and the speed of the moving object measured based on the roll angle of the moving object according to the present invention are compared to the speed (V-GPS) of the moving object measured using a GPS.

[0068] Such comparisons are performed because the speed of the moving object measured using a GPS has a small error when compared to an actual speed of the moving object. Thus, in the present invention, it is assumed that the speed of the moving object measured using a GPS is an actual speed of the moving object.

[0069] As a first comparison result, referring to FIG. 6A, it shows a graph of the speed of a moving object measured irrespective of the roll angle of the moving object according to prior art and a graph of the speed of the moving object measured using a GPS. In FIG. 6A, the horizontal axis indicates a time axis (sec.) and the vertical axis indicates a speed axis (m/s). In FIG. 6A an encircled 'a' indicates the speed (V-GPS) of the moving object measured using the GPS and an encircled 'b' indicates the speed (V-DR) of the moving object measured irrespective of the roll angle of the moving object according to prior art. Referring to FIG. 6A, when the roll angle of the moving object is neglected according to prior art, the speed (V-DR) measured according to prior art has a large difference from the speed (V-GPS) measured using the GPS. Thus, it can be seen that measurement of the speed of the moving object irrespective of the roll angle has a significant error.

[0070] Referring to FIG. 6B, it shows a graph of the speed of a moving object measured based on the roll angle of the moving object according to the present invention and a graph of the speed of the moving object measured using a GPS. In FIG. 6B, an encircled 'c' indicates the speed (V-GPS) of the moving object measured using the GPS and an encircled 'd' indicates the speed (V'-DR) of the moving object measured based on the roll angle of the moving object according to the present invention. Referring to FIG. 6B, the speed (V'-DR) measured according to the present invention has a small difference from the speed (V-GPS) measured using the GPS. Thus, a speed that is almost the same as the actual speed of the moving object can be acquired by measuring the speed of the moving object based on the roll angle of the moving object.

[0071] As a second comparison result, referring to FIG. 7A, it shows a graph of the speed of a moving object measured irrespective of the roll angle of the moving object according to prior art and a graph of the speed of the moving object measured using a GPS. In FIG. 7A, an encircled 'f' indicates the speed (V-GPS) of the moving object measured using the GPS and (e) (circled-'e') encircled 'e' indicates the speed (V-DR) of the moving object measured irrespective of the roll angle of the moving object according to prior art.

[0072] Referring to FIG. 7B, it shows a graph of the speed of a moving object measured based on the roll angle of the moving object according to the present invention and a graph of the speed of the moving object measured using a GPS. In FIG. 7B, (g) an encircled 'g' indicates the speed (V-GPS) of the moving object measured using the GPS and an encircled 'h' indicates the speed (V'-DR) of the moving object measured based on the roll angle of the moving object according to the present invention.

[0073] When FIGs. 7A and 7B are compared, a performance difference between measurement of the speed of the moving object irrespective of the roll angle of the moving object and measurement of the speed of the moving object based on the roll angle of the moving object can be seen. In other words, when the speed of the moving object is measured based on the roll angle of the moving object according to the present invention, a speed measurement error is small and a speed that is almost the same as the actual speed of the moving object can be acquired.

[0074] As described above herein, according to the present invention, the speed of the moving object can be accurately measured based on the roll angle of the moving object.

[0075] In addition, already mounted accelerometers are used without further mounting of expensive and bulky gyroscopes for measurement based on the roll angle of the moving object, thereby reducing the manufacturing cost of a DR system.

[0076] Furthermore, by accurately measuring the speed of the moving object, accuracy in positioning of the moving object using the speed of the moving object can be improved.

Claims

1. An apparatus for measuring the speed of a moving objects (30) on a road, the apparatus comprising:

accelerometers (110, 120) for measuring a first acceleration along a moving direction of the moving object (30) and a second acceleration along a lateral direction of the moving object (30);

gyroscopes (130, 140) for measuring a first angular speed along the lateral direction of the moving object (30) and a second angular speed along a lower direction of the moving object (30);

a roll angle calculator (160) for calculating a roll angle of the moving object (30) using the second acceleration, the second angular speed, a previous speed of the moving object (30) in the moving direction of the moving object (30), and a previous road inclination angle with respect to the moving direction of the moving object (30);

an inclination angle calculator (170) for calculating a road inclination angle using the calculated roll angle, the first angular speed, and the second angular speed; and

a speed calculator (180) for calculating a pure motion acceleration in the moving direction of the moving object (30) using the calculated road inclination angle and for calculating the speed of the moving object (30) using the pure motion acceleration of the moving object (30).

2. The apparatus of claim 1, further comprising a data storage unit (190) for storing the calculated road inclination angle and the calculated speed in the moving direction of the moving object (30) and for providing the previous road inclination angle and the previous speed in the moving direction of the moving object (30) to the roll angle calculator (160).

3. The apparatus of claim 1 or 2, wherein the roll angle calculator (160) uses predetermined initial values in the absence of either the previous speed in the moving direction of the moving object (30) or the previous road inclination angle with respect to the moving direction of the moving object (30).

4. The apparatus of any one of claims 1 to 3, wherein the roll angle calculator (160) arranges an equation for the second acceleration to an equation for the roll angle of the moving object (30) and substitutes the second acceleration, the second angular speed, the previous speed in the moving direction of the moving object (30), and the previous road inclination angle with respect to the moving direction of the moving object (30) into the equation for the roll angle of the moving object (30), thereby calculating the roll angle of the moving object (30).

5. The apparatus of any one of claims 1 to 3, wherein the speed calculator (180) calculates a gravitational acceleration component included in the first acceleration using the road inclination angle and subtracts the gravitational acceleration component from the first acceleration, thereby calculating the pure motion acceleration in the moving direction of the moving object (30).

6. The apparatus in accordance with any of claims 1 to 5, wherein the accelerometers (110, 120) are two axis accelerometers.

7. A method for measuring the speed of a moving object (30) on a road, the method comprising the steps of:

measuring (402) a first acceleration along a moving direction of the moving object (30) and a second acceleration along a lateral direction of the moving object (30);

measuring (404, 406) a first angular speed along the lateral direction of the moving object (30) and a second angular speed along a lower direction of the moving object (30);

calculating (408) a roll angle of the moving object (30) using the second acceleration, the second angular speed, a previous speed of the moving object (30) in the moving direction of the moving object (30), and a previous road inclination angle with respect to the moving direction of the moving object (30);

calculating (412) a road inclination angle using the calculated roll angle, the first angular speed, and the second angular speed; and

calculating (414) a pure motion acceleration in the moving direction of the moving object (30) using the calculated road inclination angle and calculating (416) the speed of the moving object (30) using the pure motion acceleration of the moving object (30).

8. The method of claim 7, further comprising storing the calculated road inclination angle and the calculated speed in the moving direction of the moving object (30).

9. The method of claim 7 or 8, further comprising calculating (408) the roll angle of the moving object (30) using predetermined initial values if there is neither the previous speed of the moving object (30) in the moving direction of the moving object (30) nor the previous road inclination angle.

10. The method of any one of claims 7 to 9, wherein the step of calculating (408) the roll angle of the moving object (30) comprises:

arranging an equation for the second acceleration to an equation for the roll angle of the moving object (30);

acquiring the second acceleration, the second angular speed, the previous speed of the moving object (30) in the moving direction of the moving object (30), and the previous road inclination angle with respect to the moving direction of the moving object (30); and

substituting the second acceleration, the second angular speed, the previous speed of the moving object (30) in the moving direction of the moving object (30), and the previous road inclination angle with respect to the moving direction of the moving object (30) into the equation for the roll angle of the moving object (30), thereby calculating the roll angle of the moving object (30).

11. The method of any one of claims 7 to 10, wherein the step of calculating (414) the pure motion acceleration in the moving direction of the moving object (30) comprises:

acquiring a gravitational acceleration component included in the first acceleration using the road inclination angle; and

subtracting the gravitational acceleration component from the first acceleration, thereby calculating the pure motion acceleration in the moving direction of the moving object (30).

Ansprüche

1. Vorrichtung zur Messung der Geschwindigkeit eines beweglichen Objekts (30) auf einer Straße, wobei die Vorrichtung umfasst:

Beschleunigungsmesser (110, 120) zur Messung einer ersten Beschleunigung längs einer Bewegungsrichtung des beweglichen Objekts (30) und einer zweiten Beschleunigung längs einer Querrichtung des beweglichen Objekts (30);

Gyroskope (130, 140) zur Messung einer ersten Winkelgeschwindigkeit längs der Querrichtung des beweglichen Objekts (30) und einer zweiten Winkelgeschwindigkeit längs einer tiefer liegenden Richtung des beweglichen Objekts (30);

einen Querneigungswinkelrechner (160) zur Berechnung eines Querneigungswinkels des beweglichen Objekts (30) unter Verwendung der zweiten Beschleunigung, der zweiten Winkelgeschwindigkeit, einer vorherigen Geschwindigkeit des beweglichen Objekts (30) in der Bewegungsrichtung des beweglichen Objekts (30) und eines vorherigen Straßenneigungswinkels bezüglich der Bewegungsrichtung des beweglichen Objekts (30);

einen Neigungswinkelrechner (170) zur Berechnung eines Straßenneigungswinkels unter Verwendung des berechneten Querneigungswinkels, der ersten Winkelgeschwindigkeit und der zweiten Winkelgeschwindigkeit; und

einen Geschwindigkeitsrechner (180) zur Berechnung einer reinen Bewegungsbeschleunigung in der Bewegungsrichtung des beweglichen Objekts (30) unter Verwendung des berechneten Straßenneigungswinkels und zur Berechnung der Geschwindigkeit des beweglichen Objekts (30) unter Verwendung der reinen Bewegungsbeschleunigung des beweglichen Objekts (30).

2. Vorrichtung nach Anspruch 1, ferner umfassend eine Datenspeicherungseinheit (190) zum Speichern des berechneten Straßenneigungswinkels und der berechneten Geschwindigkeit in der Bewegungsrichtung des beweglichen Objekts (30) und zum Bereitstellen des vorherigen Straßenneigungswinkels und der vorherigen Geschwindigkeit in der Bewegungsrichtung des beweglichen Objekts (30) für den Querneigungswinkelrechner (160).

3. Vorrichtung nach Anspruch 1 oder 2, wobei der Querneigungswinkelrechner (160) vorgegebene Anfangswerte beim Fehlen von entweder der vorherigen Geschwindigkeit in der Bewegungsrichtung des beweglichen Objekts (30) oder des vorherigen Straßenneigungswinkels bezüglich der Bewegungsrichtung des beweglichen Objekts (30) nutzt.

4. Vorrichtung nach einem der Ansprüche 1 bis 3, wobei der Querneigungswinkelrechner (160) eine Gleichung für die zweite Beschleunigung einer Gleichung für den Querneigungswinkel des beweglichen Objekts (30) zuordnet und die zweite Beschleunigung, die zweite Winkelgeschwindigkeit, die vorherige Geschwindigkeit in der Bewegungsrichtung des beweglichen Objekts (30) und den vorherigen Straßenneigungswinkel bezüglich der Bewegungsrichtung des beweglichen Objekts (30) in die Gleichung für den Querneigungswinkel des beweglichen Objekts (30) substituiert, wodurch der Querneigungswinkel des beweglichen Objekts (30) berechnet wird.

5. Vorrichtung nach einem der Ansprüche 1 bis 3, wobei der Geschwindigkeitsrechner (180) eine in der ersten Beschleunigung enthaltene Komponente der Gravitationsbeschleunigung berechnet, indem der Straßenneigungswinkel verwendet wird, und die Gravitationsbeschleunigungskomponente von der ersten Beschleunigung subtrahiert, wodurch die reine Bewegungsbeschleunigung in der Bewegungsrichtung des beweglichen Objekts (30) berechnet wird.

6. Vorrichtung nach einem der Ansprüche 1 bis 5, wobei die Beschleunigungsmesser (110, 120) Zweiachsen-Beschleunigungsmesser sind.

7. Verfahren zur Messung der Geschwindigkeit eines beweglichen Objekts (30) auf einer Straße, wobei das Verfahren die Schritte umfasst:

Messen (402) einer ersten Beschleunigung längs einer Bewegungsrichtung des beweglichen Objekts (30) und einer zweiten Beschleunigung längs einer Querrichtung des beweglichen Objekts (30);

Messen (404, 406) einer ersten Winkelgeschwindigkeit längs der Querrichtung des beweglichen Objekts (30) und einer zweiten Winkelgeschwindigkeit längs einer tiefer liegenden Richtung des beweglichen Objekts (30);

Berechnen (408) eines Querneigungswinkels des beweglichen Objekts (30) unter Verwendung der zweiten Beschleunigung, der zweiten Winkelgeschwindigkeit, einer vorherigen Geschwindigkeit des beweglichen Objekts (30) in der Bewegungsrichtung des beweglichen Objekts (30) und eines vorherigen Straßenneigungswinkels bezüglich der Bewegungsrichtung des beweglichen Objekts (30);

Berechnen (412) eines Straßenneigungswinkels unter Verwendung des berechneten Querneigungswinkels, der ersten Winkelgeschwindigkeit und der zweiten Winkelgeschwindigkeit; und

Berechnen (414) einer reinen Bewegungsbeschleunigung in der Bewegungsrichtung des beweglichen Objekts (30) unter Verwendung des berechneten Straßenneigungswinkels und Berechnen (416) der Geschwindigkeit des beweglichen Objekts (30) unter Verwendung der reinen Bewegungsbeschleunigung des beweglichen Objekts (30).

8. Verfahren nach Anspruch 7, des Weiteren umfassend Speichern des berechneten Straßenneigungswinkels und der berechneten Geschwindigkeit in der Bewegungsrichtung des beweglichen Objekts (30).

9. Verfahren nach Anspruch 7 oder 8, des Weiteren umfassend Berechnen (408) des Querneigungswinkels des beweglichen Objekts (30) unter Verwendung von vorgegebenen Anfangswerten, wenn weder die vorherige Geschwindigkeit des beweglichen Objekts (30) in der Bewegungsrichtung des beweglichen Objekts (30) noch der vorherige Straßenneigungswinkel vorhanden ist.

10. Verfahren nach einem der Ansprüche 7 bis 9, wobei der Schritt des Berechnens (408) des Querneigungswinkels des beweglichen Objekts (30) umfasst:

Zuordnen einer Gleichung für die zweite Beschleunigung einer Gleichung für den Querneigungswinkel des beweglichen Objekts (30);

Erfassen der zweiten Beschleunigung, der zweiten Winkelgeschwindigkeit, der vorherigen Geschwindigkeit des beweglichen Objekts (30) in der Bewegungsrichtung des beweglichen Objekts (30) und des vorherigen Straßenneigungswinkels bezüglich der Bewegungsrichtung des beweglichen Objekts (30); und

Substituieren der zweiten Beschleunigung, der zweiten Winkelgeschwindigkeit, der vorherigen Geschwindigkeit des beweglichen Objekts (30) in die Bewegungsrichtung des beweglichen Objekts (30) und des vorherigen Straßenneigungswinkels bezüglich der Bewegungsrichtung des beweglichen Objekts (30) in die Gleichung für den Querneigungswinkel des beweglichen Objekts (30), wodurch der Querneigungswinkel des beweglichen Objekts (30) berechnet wird.

11. Verfahren nach einem der Ansprüche 7 bis 10, wobei der Schritt des Berechnens (414) der reinen Bewegungsbeschleunigung in der Bewegungsrichtung des beweglichen Objekts (30) umfasst:

Erfassen einer in der ersten Beschleunigung enthaltenen Gravitationsbeschleunigungskomponente unter Verwendung des Straßenneigungswinkels; und

Subtrahieren der Gravitationsbeschleunigungskomponente von der ersten Beschleunigung, wodurch die reine Bewegungsbeschleunigung in der Bewegungsrichtung des beweglichen Objekts (30) berechnet wird.

Revendications

1. Appareil pour mesurer la vitesse d'un objet en mouvement (30) sur une route, l'appareil comprenant :

des accéléromètres (110, 120) pour mesurer une première accélération dans une direction de déplacement de l'objet en mouvement (30) et une seconde accélération dans une direction latérale de l'objet en mouvement (30) ;

des gyroscopes (130, 140) pour mesurer une première vitesse angulaire dans la direction latérale de l'objet en mouvement (30) et une seconde vitesse angulaire dans une direction inférieure de l'objet en mouvement (30) ;

un calculateur d'angle de roulis (160) pour calculer un angle de roulis de l'objet en mouvement (30) en utilisant la seconde accélération, la seconde vitesse angulaire, une précédente vitesse de l'objet en mouvement (30) dans la direction de déplacement de l'objet en mouvement (30) et un précédent angle d'inclinaison de la route par rapport à la direction de déplacement de l'objet en mouvement (30) ;

un calculateur d'angle d'inclinaison (170) pour calculer un angle d'inclinaison d'une route en utilisant l'angle de roulis calculé, la première vitesse angulaire et la seconde vitesse angulaire ; et

un calculateur de vitesse (180) pour calculer une accélération pure du mouvement dans la direction de déplacement de l'objet en mouvement (30) en utilisant l'angle d'inclinaison de la route calculé et pour calculer la vitesse de l'objet en mouvement (30) en utilisant l'accélération pure du mouvement de l'objet en mouvement (30).

2. Appareil selon la revendication 1, comprenant en outre une unité de stockage de données (190) pour stocker l'angle d'inclinaison de la route calculé et la vitesse dans la direction de déplacement de l'objet en mouvement (30) calculée et pour fournir le précédent angle d'inclinaison de la route et la précédente vitesse dans la direction de déplacement de l'objet en mouvement (30) au calculateur d'angle de roulis (160).

3. Appareil selon la revendication 1 ou 2, où le calculateur d'angle de roulis (160) utilise des valeurs initiales prédéterminées en l'absence soit de la précédente vitesse dans la direction de déplacement de l'objet en mouvement (30) ou du précédent angle d'inclinaison de la route par rapport à la direction de déplacement de l'objet en mouvement (30).

4. Appareil selon l'une quelconque des revendications 1 à 3, où le calculateur d'angle de roulis (160) adapte une équation pour la seconde accélération à une équation pour l'angle de roulis de l'objet en mouvement (30) et substitue la seconde accélération, la seconde vitesse angulaire, la précédente vitesse dans la direction de déplacement de l'objet en mouvement (30) et le précédent angle d'inclinaison de la route par rapport à la direction de déplacement de l'objet en mouvement (30) dans l'équation pour l'angle de roulis de l'objet en mouvement (30) et calcule ainsi l'angle de roulis de l'objet en mouvement (30).

5. Appareil selon l'une quelconque des revendications 1 à 3, où le calculateur de vitesse (180) calcule une composante d'accélération gravitationnelle incluse dans la première accélération en utilisant l'angle d'inclinaison de la route et soustrait la composante d'accélération gravitationnelle de la première accélération et calcule ainsi l'accélération pure du mouvement dans la direction de déplacement de l'objet en mouvement (30).

6. Appareil selon l'une quelconque des revendications 1 à 5, où les accéléromètres (110, 120) sont des accéléromètres à 2 axes.

7. Procédé pour mesurer la vitesse d'un objet en mouvement (30) sur un route, le procédé comportant les étapes consistant à :

mesurer (402) une première accélération dans une direction de déplacement de l'objet en mouvement (30) et une seconde accélération dans une direction latérale de l'objet en mouvement (30) ;

mesurer (404, 406) une première vitesse angulaire dans la direction latérale de l'objet en mouvement (30) et une seconde vitesse angulaire dans une direction inférieure de l'objet en mouvement (30) ;

calculer (408) un angle de roulis de l'objet en mouvement (30) en utilisant la seconde accélération, la seconde vitesse angulaire, une précédente vitesse de l'objet en mouvement (30) dans la direction de déplacement de l'objet en mouvement (30) et un précédent angle d'inclinaison de la route par rapport à la direction de déplacement de l'objet en mouvement (30) ;

calculer (412) un angle d'inclinaison d'une route en utilisant l'angle de roulis calculé, la première vitesse angulaire et la seconde vitesse angulaire ; et

calculer (414) une accélération pure du mouvement dans la direction de déplacement de l'objet en mouvement (30) en utilisant l'angle d'inclinaison de la route calculé et calculer (416) la vitesse de l'objet en mouvement (30) en utilisant l'accélération pure du mouvement de l'objet en mouvement (30).

8. Procédé selon la revendication 7, comprenant en outre l'étape consistant à stocker l'angle d'inclinaison de la route calculé et la vitesse dans la direction de déplacement de l'objet en mouvement (30) calculée.

9. Procédé selon la revendication 7 ou 8, comprenant en outre l'étape consistant à calculer (408) l'angle de roulis de l'objet en mouvement (30) en utilisant des valeurs initiales prédéterminées si ni la précédente vitesse de l'objet en mouvement (30) dans la direction de déplacement de l'objet en mouvement (30) ni le précédent angle d'inclinaison de la route ne sont disponibles.

10. Procédé selon l'une quelconque des revendications 7 à 9, où l'étape consistant à calculer (408) l'angle de roulis de l'objet en mouvement (30) comprend les étapes consistant à :

adapter une équation pour la seconde accélération à une équation pour l'angle de roulis de l'objet en mouvement (30) ;

obtenir la seconde accélération, la seconde vitesse angulaire, la précédente vitesse de l'objet en mouvement (30) dans la direction de déplacement de l'objet en mouvement (30) et le précédent angle d'inclinaison de la route par rapport à la direction de déplacement de l'objet en mouvement (30) ; et

substituer la seconde accélération, la seconde vitesse angulaire, la précédente vitesse de l'objet en mouvement (30) dans la direction de déplacement de l'objet en mouvement (30) et le précédent angle d'inclinaison de la route par rapport à la direction de déplacement de l'objet en mouvement (30) dans l'équation pour l'angle de roulis de l'objet en mouvement (30) et ainsi calculer l'angle de roulis de l'objet en mouvement (30).

11. Procédé selon l'une quelconque des revendications 7 à 10, où l'étape consistant à calculer (414) l'accélération pure du mouvement dans la direction de déplacement de l'objet en mouvement (30) comprend les étapes consistant à :

obtenir une composante d'accélération gravitationnelle incluse dans la première accélération en utilisant l'angle d'inclinaison de la route ; et

soustraire la composante d'accélération gravitationnelle de la première accélération et calculer ainsi l'accélération pure du mouvement dans la direction de déplacement de l'objet en mouvement (30).

Drawing